AWS Solution Architecture Guide

Serverless, scalable, and cost-effective AWS cloud infrastructure.

When to Use

• Designing AWS architecture for new applications
• Optimizing AWS costs
• Building serverless applications
• Creating infrastructure as code
• Multi-region deployments

Architecture Patterns

1. Serverless Web Application

Best for: SaaS platforms, mobile backends, low-traffic sites

Frontend: S3 + CloudFront
API: API Gateway + Lambda
Database: DynamoDB or Aurora Serverless
Auth: Cognito
CI/CD: Amplify or CodePipeline

Cost: $50-500/month

2. Event-Driven Microservices

Best for: Complex workflows, async processing

Events: EventBridge
Processing: Lambda or ECS Fargate
Queue: SQS (with DLQ)
State: Step Functions
Storage: DynamoDB, S3

Cost: $100-1000/month

3. Modern Three-Tier

Best for: Traditional web apps, e-commerce

Load Balancer: ALB
Compute: ECS Fargate or EC2 Auto Scaling
Database: RDS Aurora
Cache: ElastiCache Redis
CDN: CloudFront

Cost: $300-2000/month

Service Selection Guide

Compute

Service	Use Case
Lambda	Event-driven, short tasks (<15 min)
Fargate	Containerized apps, long-running
EC2	Custom configs, GPU/FPGA
App Runner	Simple container deployment

Database

Service	Use Case
DynamoDB	Key-value, serverless, <10ms latency
Aurora Serverless	Relational, variable workloads
RDS	Traditional databases
DocumentDB	MongoDB-compatible
Neptune	Graph database

Storage

Service	Use Case
S3 Standard	Frequent access
S3 IA	Backups, archives
S3 Glacier	Long-term archives
EFS	Shared file system
EBS	Block storage for EC2

Infrastructure as Code

CDK Example

import * as cdk from 'aws-cdk-lib';
import * as lambda from 'aws-cdk-lib/aws-lambda';
import * as apigateway from 'aws-cdk-lib/aws-apigateway';

export class ApiStack extends cdk.Stack {
  constructor(scope: cdk.App, id: string) {
    super(scope, id);

    const handler = new lambda.Function(this, 'Handler', {
      runtime: lambda.Runtime.NODEJS_18_X,
      code: lambda.Code.fromAsset('lambda'),
      handler: 'index.handler',
    });

    new apigateway.LambdaRestApi(this, 'Api', {
      handler,
    });
  }
}

CloudFormation Snippet

Resources:
  MyFunction:
    Type: AWS::Lambda::Function
    Properties:
      Runtime: nodejs18.x
      Handler: index.handler
      Code:
        S3Bucket: !Ref CodeBucket
        S3Key: function.zip
      MemorySize: 256
      Timeout: 30

Cost Optimization

Quick Wins

• Enable S3 Intelligent-Tiering
• Use Savings Plans for predictable workloads
• Set CloudWatch log retention (7-30 days)
• Use VPC endpoints instead of NAT Gateway
• Right-size Lambda memory

Cost Breakdown Tips

• Enable Cost Explorer
• Set up billing alerts
• Tag all resources for tracking
• Review NAT Gateway traffic
• Check data transfer costs

Security Best Practices

Practice	Implementation
Least Privilege	IAM roles with minimal permissions
Encryption	KMS for at-rest, TLS for transit
Network Isolation	Private subnets, security groups
Secrets	Secrets Manager, not hardcoded
API Protection	WAF, rate limiting, API keys
Audit Logging	CloudTrail, VPC Flow Logs

Startup Stages

MVP ($20-100/month)

• Amplify full-stack
• Lambda + API Gateway + DynamoDB
• Cognito for auth
• S3 + CloudFront for frontend

Growth Stage ($500-2000/month)

• Add ElastiCache
• Aurora Serverless for complex queries
• CloudWatch dashboards and alarms
• CI/CD pipeline
• Multi-AZ deployment

Scale-Up ($3000-10000/month)

• Multi-region deployment
• DynamoDB Global Tables
• WAF and Shield
• Advanced monitoring (X-Ray)
• Reserved capacity

Common Pitfalls

• Over-engineering early - Don't build for 10M users with 100
• Public S3 buckets - Block public access
• Overly permissive IAM - Avoid * permissions
• No caching - Add CloudFront early
• NAT Gateway costs - Use VPC endpoints